Don't be hasty in discarding old gear. You can only carry a limited number of equipment in your inventory at any one time. So ideally, you'll want to get rid of the old stuff to make room for new ones. However, keep in mind that you can use those old gear to upgrade your new stuff, which is a by far better alternative as opposed to selling them in return for some measly gil.
Use Mythril wisely. Mythril is without a doubt one of the most valuable items in the game. One that has a whole lot of uses but is not as easy to come by. While Mythril can be used to purchase additional ability and equipment slots for your characters, or to continue with bonuses when you are defeated in battle, it is still best saved for use on nothing but rare relic draws (5 Mythril per draw) in hopes of scoring some powerful new gear.
Take advantage of the Synergy System. As discussed in the game's tutorial level, characters and gear can get significant stat boosts when used in realms from which they originated. For example, if Cloud uses any gear marked "VII", that gear will be boosted. At the same time, if you were to take Cloud to battle in dungeons within the FFVII realm, he toowill be stronger.
Force quit the game if must retry a battle. Should things go awry in the midst of battle and you feel the need to regroup, simply quit the game then run it again. Once loaded, you'll be asked if you wish to continue with battle that was interrupted. Just give the affirmative and you're back in business.
Complete the Daily Dungeons. This is where you get to collect the orbs necessary to create abilities, gain much higher experience points to level up your characters, and rack up on gil. You also get to receive a bonus Mythril for mastering each of the difficulties too. These dungeons change everyday.
Complete the Special Events. These events don't show up all that often and are only available for a limited period of time when they do appear This is where you get to recruit new party members (usually just one character per event), receive new gear (occasionally), and replenish your Mythril.
Take advantage of the Roaming Warrior Feature. Added in the version 4.0.2 update, this feature allows you to summon the chosen characters of other players and use their Soul Breaks in battle. Should you find a certain character that you really like, you can follow that player and his/her character will always be available in your Roaming Warriors list. Alternately, you can enter your friends' code in the "Find Friends" tab (under "Friends" tab in the menu) and their character will be added to your list of warriors.
Complete Quests for Rewards. Another new feature made available in version 4.0.2. These are extra tasks you can complete for rewards, including Mythrils, Orbs, Growth Eggs and Equipment Upgrade Materials. The "Quest" option is located at the top-right corner of the "Realms" selection screen.
